180 deg. h-plane bend for rectangular waveguide



April 2, 1963 J. F. REuvERs ET AL 3,084,296

180 H-PLANE BEND FOR RECTANGULAR wAvEGUIDE Filed Oct. 23, 1961 5 Sheets-Sheet l 11PM# Hm April 2, 1963 J. F. REUvERs ETAL 3,084,296

18o' H-PLANE BEND FOR RECTANGULAR WAVEGUIDE Filed Oct 23, 1961 5 Sheets-Sheet 2 y 1PM 2( 24W April 2, 1963 J. F. REUvERs ETAL 3,084,296

180' H-PLANE: BEND FOR RECTANGULAR WAVEGUIDE Filed om.l 23, 1961 3 Sheets-Sheet 5 lite rates Bgh Patented Apr. 2, 1953 3,034,296 180 H-PLANE BEND FOR RECTANGULAR WAVEGUIDE .lohn F. Reuvers, Santa Ana, .lames U. Clark, La Habra,

and Edward W. Loclf art, Buena Park, Calif., assignors to Hughes Aircraft Company, Culver City, Calif., a

corporation of Delaware Filed Get. 23, 1951, Ser. No. 148,305 9 Claims. (Cl. S33- 90) This invention relates to microwave devices and more particularly to a rectangular wave-guide structure which edects :a 180 bend in the H-plane.

A conventional H-plane bend for rectangular waveguide generally constitutes :two sections of waveguide having a common narrow side and a semicircular .termination extending from the outer narrow sides. The construction tof this type of H-plane bend, however, is somewhat diiiicult to realize in `that it is generally desirable to employ investment castings which inherently have several significant shortcomings. Performance requirements, for example, may dictate tolerances which are Sulliciently rigid as to make the castings very diticult lto produce in quantity. In addition, the castings often show tendencies toward warp/age when subjected to a dip brazing process which may be necessary to incorporate the bend into a more extensive waveguide system.

It is therefore an object of the present invention to provide an improved 180 H-plane bend in rectangular waveguide having a low voltage standing-wave ratio over a broad range of frequencies.

Another object of :the present invention is to provide a 180 H-plane bend for rectangular waveguide :that is comparatively simple to manufacture.

Still another object of the present invention is to provide a 180 H-plane bend for rectangular waveguide that has a low insertion loss over a broad range of frequencies.

A further object of the present invention is to provide a 180 H-plane bend for rectangular waveguide that requires a minimum amount of space.

-In accordance with the present invention, the narrow sides lof first and second rectangular waveguide sections are disposed adjacent and coextensive each other and are separated by a conductive spacer which may be several times the thickness of the waveguide wall. A shouting plane is disposed across the extremities of the waveguide and -a rectangular aperture placed through the adjacent narrow sides of the waveguide and the spacer in the vicinity near and normal to the shouting plane, This aperture is slightly reduced in height from that of the waveguide to achieve rigidity Iand simplicity of manufacture. This reduction in height, however, introduces capacitive reactance which, in turn, is neutralized by shortening the aperture to the extent that an equal a-nd opposite amount of inductive reactance is introduced. Lastly, inductive elements are disposed symmetrically about each 90 bend in a manner to render the bend reflectionless 'over a wide range of frequencies. In a preferred embodiment of the invention, inductive irises are employed in which case the placement and penetration are chosen to render the bend reectionless.

In the operation of the `180" H-plane bend of the present invention, the rectangular yaperture `of the present invention appears resonant over a broad range of frequencies, the width of which is enhanced by the conductive spacer. In addition, the 90 bend in either waveguide appears as a shunt capacitance at the plane of its bend. This shunt capacitance, together with lthe shunt induct-ance of the inductive elements, produces resonance through the remiander of the H-plane bend.

The above-mentioned and other features and objects of this invention and the manner of obtaining them will become more apparent by reference to the following description taken in conjunction with the accompanying drawings, wherein:

FIGURE l is a perspective View, partially cutaway, of a preferred embodiment 'of the invention;

FIG. 2 is a plan sectional view -of the device of FIG. 1;

FIG. 3 is a View of section 3 3' of FIG. 2; and

FIGS. 4 and 5 are perspective views of alternate embodirnents of the device of the present invention.

Referring now to FIGURE 1 of the drawings, a preferred embodiment oi the present invention includes sections 10, 12 of rectangular waveguide, the extremities only :of which are shown. The section 10 of rectangular waveguide has parallel narrow sides 13, 14 and parallel broad sides 15, 16. Similarly, the section 12 of rectangular waveguide has parallel narrow sides 17, 18 and parallel broad sides 19, 20. The narnow sides i114, y17 of the sections 10, 12 of rectangular waveguide, respectively, 'are disposed adjacent and coextensively andare separated with a conductive I-beam spacer 22. The internal height of the Lbeam spacer 22 is made equal to the extern-al Width of the narrow sides 14, y17 thereby to accommodate both sections 10, 12 and separate the narrow sides 14, 17 by only the thickness of the vertical portion of I-beam spacer 22, as viewed in the drawing. The Ibeam spacer '.22 extends back from the extremities of the sections 10, 12 .of rectangular waveguide by an amount greater than the width of section 10 or 12. A rectangular aperture 24 is then disposed through the adjacent narrow sides 14, 17 of sections 10, 12 of rectangular waveguide, respectively, and through the I-beam spacer 22. The aperture 24 commences at a `distance equal to the width of the waveguide sections 10, 12 from 4the extremities thereof and continues toward the extremities for a distance substantially equal to 90% of the width of the waveguide section 10 or 12. The height of the rectangular Iaperture 24, .on .the other hand, is `of the order of of the inner height of the sections 10, 12 of rectangular waveguide and is disposed symmetrically therein. In general, a length tof the rectangular aperture 24 that is less than the Width of the waveguide sections 10, 12 introduces an inductive reactance and a height that is less than the height of the waveguide sections 10, 12 introduces a capacitive reactance. It is nevertheless desir-able to make the height of Ithe rectangular aperture 24 suliicient-ly less than the height of the waveguide sections 10 for 12 for ease `of manufacture and to achieve rigidity in the structure. The length and width of the rectangular apenture are accordingly selected so .as to introduce equal amounts of reactance and accordingly make the aperture 24 resonant. The characterisitc of this resonance is broadened by the increased thickness of the aperture 24 produced by the I-beam spacer 22.

In addition to the foregoing, irises 26, 27 are inserted transversely into the waveguide sections 10, 12. from the narrow sides 13, 18, respectively, at corresponding points therealong which points occur within the center portion of the length of rectangular aperture 241. Further, irises 28, 29 are inserted longitudinally into the center portion of waveguide sections 10, 12, respectively, from the extremities thereof equidistant from the I-bearn spacer 22. The lengths of the irises 26, 27, 28, 29 are substantially the same and are of the order of 25% of the width of the rectangular waveguide section 10 or 12. Lastly, a shorting bar 30 is disposed across the common extremities of rectangular waveguide sections 10, 12 immediately adjacent extremities of the irises 28, 29. In order to increase the rigidity of the bend, shorting bar 30 may, for example, have a square cross section. Final assembly of the device may be achieved by employing a dip brazing process to weld the respective elements together.

rnencingV from'the extremities of the waveguide sectionsv 10, 12 extends from 0.1A to A. The irises 26, 27 extend `transversely inward commencing fro-rn the narrow sides 13, 18 at a distance of 0.5A from the extremities of the waveguide sections 10, 12 and theirises 28, 29 each extend inwardly from the shorting'bar 30 longitudinally along the center line of the waveguidesections 10, 12, respectively. In each case the irises 26;' 27, 28, 29 are of the order of 025A in length and extend for theentire distance between the broad sides 15, 16-and 1.9,A 20 of the waveguide sections 10, 12, respectively. Referring to FIG. Y 3, onV the other hand, wherein the distance between thebroad sides 15, 16 or 19, 207is designated I-I, the height of the aperture 24'is designated 0.8H and is disposed equidistant from the broad sides 15, 16 and 19, 20,

Referring nowv to FIG. 4, thereis shown an alternate embodiment of the device of FIG. 1-wherein the irises 26,27, 28, 29 'are replaced'with conductive cylindrical posts-36, 37, 38, 39, respectively. The conductive cylin-l drical posts 36, 37, 38, 39 arefgeneraliy disposed normal to` the broad sides 15, 16, 19, 20; arey of a diameter-of from 0.1A to 0.25A; and arev disposed with a diameter thereof coinciding with a line which corresponds to the position of the respective irises 26, 27, 28, 29 with the respective peripheries thereof butting upKV against the narrow sides -12, 13 and the snorting bar 3i?. This latter position is" determined by the diameter of the respective conductive cylindrical posts 36, 37, 38, 39 in that different dia-meters -correspond to different inductivereactances.

The remainder of theadevice of' FIG. 4 is similar to that of FIG. l.

Referringto FIG. 5, there Vis shown an additional device in -accordance with the present invention wherein the -irises 26, 27, 28, 29v are replaced with se-micircular'conductive posts 4i), 41, 42, 43respectively. The-respective semicircular conductive postsare generally of the samen radius which is from 0.1A to 025A and are disposed with the at sides thereof adjacent the narrow walls 13', 18 or the shorting bar 30 with the centers thereof placed at points corresponding to the junctions where the irises 26,

27, 28,29 abut against the narrow walls 12, 13 and shortn4 ing bar 30.- As before, the remainder of the device of FIG. 5 is similar to that of FIG. l.

In the operation of a 180 I-I-plane bend offa type parent to those skilled in the art that various changes in form and arrangement of parts may be made to suit requirements without departing from the spirit and scope' o-f the invention. Y

What is claimed is: 1. A microwave device comprising first and second sections of rectangular waveguide of predetermined height and width, a narrow side of said first section of rectangular waveguide being disposed adjacent Aand coextensiveV with a narrow side of said second `section of rectangular waveguide; a Longitudinalv aperture joining said firstsection of rectangular waveguide with said second sectionl of rectangular waveguide through said adjacent narrowV sides; first and second inductive elements disposed inthe center region of the broad sides of said first and second sections of rectangular waveguide, respectively, at corresponding points therealong opposite one extremity of said longitudinal aperture; and third and fourth inductive elements disposed adjacent the remaining narrow walls of said first and second sections of rectangular waveguide, respectively, at corresponding points therealong opposite the center portion of said longitudinal aperture.

2. The microwave device as defined in claim l where` in said longitudinal aperture presents substantially equal amounts of inductive and capacitive reactance throughout a broad range of frequencies.

3. The microwave device as defined in claim l which additionally includes means for providing a shorting plane transversely across said first and second sections of rectanguiar waveguide adjacent to said first and second inductive elements and on the side thereof opposite from said third and fourth inductive elements.

4. The microwave device as defined in claim l wherein said first, second, third and fourth inductive elements are conductive circular posts extending between the respective broad sides of said first'and second rectangular waveguide sections.

5. The microwave device as defined in claim l wherein said first, second, third and fourth inductive elements vare conductive semi-circular posts extending-between the respective 4broad sides of said firstA and second rectangular waveguide sections, the fiat side of said first and second inductive ele-ments beingnormal to said longitudinal aperture and on the side' of said semi`circular posts that is farthest therefrom, and the flat side of said third and ourthinductive elements being `immediately adjacent the respective'remaining narrow walls of said first and second sections of rectangular waveguide.-

6. An H-planeV bendfor rectangular waveguide comprising first and second sections of rectangular-waveguide of predetermined'height and width, a narrow side of said first section of rectangular waveguide being disposediadjacent to and coextensive with a narrow side of said second section of rectangular waveguide; means for providing a'shorting plane transversely across said first and second sections of rectangular waveguide; a resonant aperture having a height `and width less than said predetermined height and width, respectively, joining said first and second sections of rectangular waveguide through said adjacent narrowsides thereof adjacent said shorting plane; first and second conductive irises of a Iheight substantially equal to said predetermined height disposed in 'thewcenter region of said first 'andv second rectangular and 'extending awayV therefrom on 'the sameside as said resonant aperture; and third and fourth' conductive irises of -aheight substantiallyV equal to said predetermined height'eXtending inwards from corresponding points of the remaining" narrow sides of said first and second sections of rectangular waveguide, respectively, transversely to the longitudinal axis thereof and opposite the center portion of said resonant aperture.

7.` The H-plane 180 bend for rectangular waveguide as defined in claim 6 wherein said first, second, third and fourth iriscs each have a substantially uniform length of from 0.15 to 0.40 times said predetermined width.

8; The H-plane 180 bend for rectangular waveguide as defined in claim 6 wherein said` resonant aperture has 4a rectangular configuration.

9. The I -I-plane 180 bend for rectangular waveguide as defined in claim 8 wherein said rectangular configuration has a length of from 0.80 to 0.95 times said predetermined width and a height of from 0.7 to 0.9 times said *predetermined` height.

No references cited. 

1. A MICROWAVE DEVICE COMPRISING FIRST AND SECOND SECTIONS OF RECTANGULAR WAVEGUIDE OF PREDETERMINED HEIGHT AND WIDTH, A NARROW SIDE OF SAID FIRST SECTION OF RECTANGULAR WAVEGUIDE BEING DISPOSED ADJACENT AND COEXTENSIVE WITH A NARROW SIDE OF SAID SECOND SECTION OF RECTANGULAR WAVEGUIDE; A LONGITUDINAL APERTURE JOINING SAID FIRST SECTION OF RECTANGULAR WAVEGUIDE WITH SAID SECOND SECTION OF RECTANGULAR WAVEGUIDE THROUGH SAID ADJACENT NARROW SIDES; FIRST AND SECOND INDUCTIVE ELEMENTS DISPOSED IN THE CENTER REGION OF THE BROAD SIDES OF SAID FIRST AND SECOND 